What's the obsession with Union Square? The Gap Fillers? Union Square is not the cause of bottlenecking on Lexington Ave.
According to TA personnel who report to this board, the TA thinks it is. It's a convenient bottleneck because it would take multi-millions to repair.
I'll look up the number of TPH that currently run on Lexington. I did this last pick, and posted those numbers. I'd say 25 TPH is the max Lexington can handle. Even if you can develop a signal system that's better than the current one, there are just too many daily occurances on Lexington that prevent the TA from having more trains on the road.
I will agree that, if the TA send out only 25 tph that it is fairly difficult to acieve greater service levels than 25 tph. I have been intrigued by the variability in headway for trains on the Lex because, if the trains ran near identical profiles then 40 tph operation would be possible. I've tried following chasing up the Lex to find the source of the variability. The interlocking at 138th St is certainly a big problem. However, my observations at E 180th St would indicate that major problems when the trains leave the box.